Since the 1940's both the incidence and mortality rates for AML have been increasing. Exposure to medical x-rays is the factor most likely to account for the greatest proportion of this increase. We propose to expand an ongoing population-based study of this hypothesized association designed to overcome the serious limitations of previous case-control studies. We will include 450 Los Angeles County cases aged 30-69 with AML diagnosed from 1987-1995 and 450 individually matched neighborhood controls. We will obtain personal interview data for 272 cases, all 450 controls, and interview data from proxy respondents for 628 subjects (cases and controls). We will also abstract information from medical charts on x-ray and drug exposures during the 10 years prior to diagnosis date. We plan to develop improved radiation dosimetry models that consider type of examination, year performed, type of facility and retake rate. Comparisons of data sources (i.e. self/proxy; interview/chart) will allow estimation of error rates and correction for misclassification. Uncertainty estimates will be incorporated into logistic regression analyses. We hope to identify which procedures, if any, are associated with excess risk so that appropriate precautions can be taken against indiscriminate use. Our preliminary findings and those from previous case-control studies suggest that AML risk relates to multiple repeat spinal x-rays and GI series (with fluoroscopy).